1. Field of the Invention
The present invention relates to an occupant restraint system for protecting occupants sitting in vehicle front seats.
2. Description of the Related Art
Occupant restraint systems, such as seat belts and airbags, for protecting a vehicle occupant in case that the vehicle impact applies a given or greater impact load due to a collision with another vehicle, obstacle or the like, have been well known.
One of such occupant restraint systems is a knee airbag that is inflated near the occupant's knees to protect the knees. The knee airbag is installed independently of an upper-body airbag for protecting the occupant's upper body.
The knee airbag is inflated the given time earlier than the upper-body airbag, to thereby prevent the occupant's knees from hitting against the instrument panel or the occupant's body from sliding under the instrument panel. Moreover, the knee airbag restrains the occupant's knees to lock his/her lower body, so that the occupant's upper body that is bent at his/her lumber part is received by the upper-body airbag at the best angle for occupant protection. An occupant restraint system provided with such a knee airbag is disclosed in Unexamined Japanese Patent Publication No. H01-156155 (hereinafter referred to as Patent Document 1).
In the occupant restraint system disclosed in the Patent Document 1, a knee airbag and an upper-body airbag are both inflated every time the vehicle is applied with the given or greater impact load. Therefore, even if a collision occurs when the vehicle runs at relatively low speed, and a seat belt is then sufficient for the protection of the upper body, both the knee and upper-body airbags are inflated.
In the event of low-speed collisions, however, the vehicle often remains capable of running after the collision. In such cases, if the upper-body airbag is inflated at the same time as mentioned above, this causes the problem that the upper-body airbag obstructs the occupant's vision, making the driving after the collision difficult.